Secure printing systems are often utilized when printing secure value documents such as postage, tickets and money orders. Since such documents may have substantial cash value, there exists a continuing problem of preventing the copying of such documents to generate fraudulent documents. Several different types of security features are used to secure such documents. In postage printing systems, 2 dimensional barcodes may be used to securely carry information used as proof of postage payment during mail processing. A DATAMATRIX barcode may be used and as such the postage printer will print a 2D DATAMATRIX barcode to create a secure indicium as evidence of postage payment.
Since the security features enable the detection of copies of the secure value documents, it is necessary to ensure that the secure printing systems themselves cannot be used to print fraudulent images which contain the security features. It is therefore necessary to control the source of the images being printed by the secure printing systems, thereby preventing a dishonest person from providing a fraudulent image, e.g., a counterfeit postage indicium, ticket, money order or the like, to the secure printing system, which will print the security features in the fraudulent image, such that it appears legitimate. As a result, such secure printing systems are single purpose devices, i.e., they can only be used to print value documents from a secure source and cannot be used to print any other types of images. This restriction limits the usefulness of such secure printing systems. Personal postage stamp printers have been proposed. With such printers, postal customers, after prepayment of postage, will be allowed to print adhesive postage stamps. The postal customers will be permitted to create or supply a custom image to be incorporated as part of the postage stamps. For example, a postage label printer may be able to print secure postage labels with custom images, but not other non-secure text or graphics since that might allow fraudulent copies of valid postage indicia to be printed.
Personal postage stamp printers may utilize direct contact thermal printhead technology. Thermal printheads are available from several companies including Kyocera Industrial Ceramics Corp. of Vancouver, Wash. and Mitsubishi Electric of Irvine, Calif. Such printheads are available in a variety of sizes and geometric configurations and may be purchased in custom configurations including those having width of approximately one inch. In such printers, the printheads are typically designed to produce heat using thermal printhead heating elements in order to activate thermal media such as a thermal media label stock. Such thermal media is often gray scale media and the elements are heated to higher levels to produce a darker gray output on the thermal media label stock. The thermal printhead typically includes a linear array of resistive heating elements that are brought to increased temperatures using increased drive current. The thermal media passes over the linear array and portions of the media are activated due to the heat present at each heater element.
Thus, there exists a need for a printing system that can be used to print both secure value documents and non-secure documents while ensuring that fraudulent copies of secure value documents printed by the printing system can be prevented.